There is a great need for copper alloys for electrical application purposes. These alloys are required, inter alia, as materials for electronic components, in particular semiconductor carriers for transistors, integrated circuits or the like, and parts for electrical systems for cars.
Materials for electronic components, in particular semiconductor carriers of the type mentioned (so-called lead frames), must exhibit particular combinations of properties:
(a) The electrical and thermal conductivity should be as high as possible (for example, above 65% IACS);
(b) High mechanical strength is required, together with sufficient bendability;
(c) In addition, a high degree of resistance to softening is required. In this connection, a measure of the resistance to softening is the so-called semihardening temperature T.sub.H, which is obtained from the softening curve (Vickers hardness HV as a function of the annealing temperature T). In this connection, the semi hardening temperature T.sub.H is correlated with the value ##EQU1##
(d) There is to an increasing extent a requirement for homogeneous materials, i.e. materials the structure of which does not include any coarse precipitates or inclusions. This leads on the one hand to a perfect connection between the so-called bonding wires and the semiconductor carrier, and on the other hand, if required for the further processing steps, satisfactory properties regarding galvanic or chemical surface refinement.
Iron-nickel alloys or copper alloys, such as for example CuFe2P (C 19400) or CeFeSnP (C 19520), inter alia, have to date been employed to a large extent for the abovementioned case of application. Even in the case of the abovementioned copper alloys, in particular the electrical conductivity and, because of the relatively high alloy proportion, which in some cases leads to undesirably coarse precipitates, also the homogeneity of the materials still leave something to be desired.
For connecting components in electrical systems for cars, because of the high current loading, there is a requirement for a material with the highest possible electrical and thermal conductivity, with at the same time high strength and thus sufficient mechanical stability, as well as improved corrosion resistance in relation to brass alloys. In addition, it should be possible to produce the material at low cost.
The object of the invention is, accordingly, to provide a copper alloy which, in particular for the abovementioned fields of application, exhibits particularly favorable properties at a relatively low price.